Show a helpful error if the gstofa plugin isn't available

src/musicbrainz/fingerprinter.cpp

@@ -32,6 +32,16 @@ Fingerprinter::~Fingerprinter() {
   delete event_loop_;
 }
 
+bool Fingerprinter::GstreamerHasOfa() {
+  GstElementFactory* factory = gst_element_factory_find("ofa");
+  if (!factory) {
+    return false;
+  }
+
+  gst_object_unref(factory);
+  return true;
+}
+
 GstElement* Fingerprinter::CreateElement(const QString &factory_name,
                                        GstElement *bin) {
   GstElement* ret = gst_element_factory_make(

src/musicbrainz/fingerprinter.h

@@ -37,6 +37,9 @@ public:
   Fingerprinter(const QString& filename);
   ~Fingerprinter();
 
+  // Checks if this gstreamer installation has the required ofa plugin.
+  static bool GstreamerHasOfa();
+
   // Creates a fingerprint from the song.  This method is blocking, so you want
   // to call it in another thread.  Returns an empty string if no fingerprint
   // could be created.

src/ui/edittagdialog.cpp

@@ -23,6 +23,7 @@
 #include "core/utilities.h"
 #include "library/library.h"
 #include "library/librarybackend.h"
+#include "musicbrainz/fingerprinter.h"
 #include "playlist/playlistdelegates.h"
 #include "ui/albumcoverchoicecontroller.h"
 #include "ui/coverfromurldialog.h"
@@ -59,7 +60,7 @@ EditTagDialog::EditTagDialog(QWidget* parent)
   connect(cover_loader_->Worker().get(), SIGNAL(ImageLoaded(quint64,QImage,QImage)),
           SLOT(ArtLoaded(quint64,QImage,QImage)));
   connect(tag_fetcher_, SIGNAL(ResultAvailable(Song, SongList)),
-          results_dialog_, SLOT(FetchTagFinished(Songa, SongList)),
+          results_dialog_, SLOT(FetchTagFinished(Song, SongList)),
           Qt::QueuedConnection);
   connect(tag_fetcher_, SIGNAL(Progress(Song,QString)),
           results_dialog_, SLOT(FetchTagProgress(Song,QString)));
@@ -69,7 +70,6 @@ EditTagDialog::EditTagDialog(QWidget* parent)
   ui_->setupUi(this);
   ui_->splitter->setSizes(QList<int>() << 200 << width() - 200);
   ui_->loading_container->hide();
-  ui_->fetch_tag->setVisible(false);
 
   // An editable field is one that has a label as a buddy.  The label is
   // important because it gets turned bold when the field is changed.
@@ -679,6 +679,11 @@ void EditTagDialog::ResetPlayCounts() {
 }
 
 void EditTagDialog::FetchTag() {
+  if (!Fingerprinter::GstreamerHasOfa()) {
+    QMessageBox::warning(this, tr("Error"), tr("Your gstreamer installation is missing the 'ofa' plugin.  This is required for automatic tag fetching.  Try installing the 'gstreamer-plugins-bad' package."));
+    return;
+  }
+
   const QModelIndexList sel = ui_->song_list->selectionModel()->selectedIndexes();
 
   SongList songs;

src/ui/mainwindow.cpp

@@ -45,6 +45,7 @@
 #include "library/librarydirectorymodel.h"
 #include "library/libraryfilterwidget.h"
 #include "library/libraryviewcontainer.h"
+#include "musicbrainz/fingerprinter.h"
 #include "musicbrainz/tagfetcher.h"
 #include "playlist/playlistbackend.h"
 #include "playlist/playlist.h"
@@ -1887,6 +1888,11 @@ void MainWindow::Exit() {
 }
 
 void MainWindow::AutoCompleteTags() {
+  if (!Fingerprinter::GstreamerHasOfa()) {
+    QMessageBox::warning(this, tr("Error"), tr("Your gstreamer installation is missing the 'ofa' plugin.  This is required for automatic tag fetching.  Try installing the 'gstreamer-plugins-bad' package."));
+    return;
+  }
+
   // Create the tag fetching stuff if it hasn't been already
   if (!tag_fetcher_) {
     tag_fetcher_.reset(new TagFetcher);